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Quite often people disparage Seiko (and Rolex to a lesser extent) because they have persevered with 'narrow' 20 mm bracelets on some of their dive watches. The fashion these days is clearly for wider 22 mm and even 24 mm bracelets, but maybe Seiko and Rolex have a functional reason for retaining narrow lug widths on their professional watches.

The spring bars are one of the weakest points in the watch baracelt, maybe the weakest. I'm no structural engineer, but intuitively it seems that a short spring bar will be stronger than a long one. Like a short bridge is stronger than a long one.

So maybe Seiko and Rolex have intentionally resisted the wide barcelet trend to keep their professional series watches as tough as possible?
 

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So maybe Seiko and Rolex have intentionally resisted the wide barcelet trend to keep their professional series watches as tough as possible?

That, and they've prevented their brands from becoming clown watches, utilising huge steel wrist cuffs that look like they belong in a bondage cave.
 

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You might be right, Jason!
I think a narrow bracelet will put less stress and torque on the springbars.
But, from an aesthetic point of view, many wide bracelets look just too wide.
Of course, the size of the case is imortant. A 38mm case looks good on a 19mm bracelet, 40-42mm case on a 20-21.
A 45mm case lokks just perfect with a 24mm bracelet.
I wonder if Panerai (most are 44 or 45mm) did away with the spring bars because of it's weakness?
 

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All true dive watches are subjected to the same testing under ISO 6425. The bracelet or strap is pulled with 45 lbs of force regardless of what length the spring bars are. Rolex remains with the same size bracelet because their watches look good and people buy them.
 

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That, and they've prevented their brands from becoming clown watches, utilising huge steel wrist cuffs that look like they belong in a bondage cave.
Now that's funny.:-d:-!
 

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Quite often people disparage Seiko (and Rolex to a lesser extent) because they have persevered with 'narrow' 20 mm bracelets on some of their dive watches. The fashion these days is clearly for wider 22 mm and even 24 mm bracelets, but maybe Seiko and Rolex have a functional reason for retaining narrow lug widths on their professional watches.

The spring bars are one of the weakest points in the watch baracelt, maybe the weakest. I'm no structural engineer, but intuitively it seems that a short spring bar will be stronger than a long one. Like a short bridge is stronger than a long one.

So maybe Seiko and Rolex have intentionally resisted the wide barcelet trend to keep their professional series watches as tough as possible?
Seiko has made many of their ISO divers with 22mm lugs....6309, 7040, SBBNs and most of the SKX models, some SARBs.

Seiko's fat springbars are the hardest to get off of a watch IMO. I think the logic is there, but the springbar makes a significant difference and between 20-22, it becomes irrelevant with a solid springbar
 

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While simple bending of the hollow tube plays a part, construction and quality have a larger influence on how much load a spring bar will hold.

If you look at the attached drawings of a spring bar, you will see the uniform load of the strap (purple) must be countered by a equal and opposite load at the pin end (red). Since the end piece is loose inside the tube, the crimp at the end of the tube will act as a fulcrum (blue). (The distance from the red load to the fulcrum is more or less constant, as this is governed by how much shortening is required to fit a standard length spring bar in a standard width lug.)

The distance from the end to the fulcrum will create a moment (tan).

The moment will form a couple (green) with one force acting at the inside end of the end piece, and the other force acting on the crimp, attempting to force it open (light blue)

How far the end piece extends into the tube (gray) and how resistant the crimp is to deformation will be more critical to the total load a spring bar can withstand than the simple bending of a hollow tube under uniform load.

- A thinner tube will resist less than a thick tube.

- A long end piece will resist more than a short one.

- And a stronger material chosen for the tube will resist deformation better.

- Some really cheap spring bars are made with rolled tube instead of a seamless tube, a seamless tube will be much stronger.
 

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